The polyphenylene ethers and processes for their preparation are known in the art and described in numerous publications, including Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875 or Spousta, U.S. Pat. No. 3,549,670. Other procedures are described in the Bennett and Cooper patents, U.S. Pat. Nos. 3,639,656, 3,642,699, 3,733,299 and 3,661,848. All of these patents are incorporated herein by reference.
The processes most generally used to produce the polyphenylene ethers are based on the self-condensation of a monovalent phenol in the presence of an oxygen-containing gas and a copper-amine catalyst.
In the prior art, various extraction techniques have been proposed which use many different reagents that form complexes with the copper-amine catalyst. For the most part, the complexes of the prior art extraction methods have been completely or partially soluble in the reaction solution. Therefore, the efficiency of these extraction type separations is always dependent on the solvent partition ratio and necessitates the use of large volumes of liquid for liquid-liquid extraction of the reaction solution. These increase the cost of the operation by reason of the problems associated with the handling, storage and purification of large volumes of liquids. In view of this, it is apparent that it would be desirable to have a catalyst separation process that eliminates the need to employ large quantities of liquid in various prior art types of liquid-liquid extraction processes.
Polyethylene ether reaction solutions contain polymer, catalyst, an organic solvent and some water formed in the reaction. This system inherently poses problems if one seeks to insolubilize the catalyst as many materials that are insoluble in organic liquids are soluble in water.
Applicants have discovered that when 2,2'-dipyridyl is added to a polyphenylene ether reaction solution that contains a copper-amine catalyst, a complex is formed that is insoluble in the organic reaction solvent and in water. This permits the subsequent separation of the complexed catalyst without the use of any liquid-liquid extraction technique.
Accordingly, it is a primary object of this invention to provide a method of separating a copper-amine catalyst from a polyphenylene ether reaction mixture that does not require liquid-liquid extraction of the catalyst.
It is also an object of this invention to provide a method of making the copper-amine catalyst of a polyphenylene ether reaction mixture insoluble in both the organic and aqueous phases of said reaction mixture.